Don't Box Values in PrimitiveDictionaryBuilder

[tustvold]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.

PrimitiveDictionaryBuilder constructs Box<u8> for its values, despite them being a known size. This appears to be a workaround for types such as f32 not implementing Hash or Eq

Describe the solution you'd like

Construct a newtype wrapper that implements Eq and Hash using ToByteSlice.

Describe alternatives you've considered

Additional context